Rolling bearing in aircraft

ABSTRACT

A single-row or multi-row rolling bearing comprising thin-walled bearing races which are made of a martensitic, through hardened steel and have the following characteristics: a surface hardness of ≧613 HV (56 HRC) in the area of the bearing face; a core hardness of ≧285 HV (28 HRC); a difference of ≧150 HV (9 HRc) between the surface hardness and the core hardness. The core hardness is reached at a depth ranging between 8 percent of the diameter of the rolling elements and 90 percent of the wall thickness on the bottom of the track. There is a ratio of ≧20 between the diameter of a pitch circle T k  and the diameter of a rolling element D W .

CROSS REFERENCE TO RELATED APPLICATION

The present application is a 35 U.S.C. §§ 371 national phase conversionof PCT/DE2003/003603 filed 29 Oct. 2003, which claims priority of GermanApplication No. 102 50 459.8 filed 30 Oct. 2002. The PCT InternationalApplication was published in the German language.

FIELD OF THE INVENTION

The invention relates to a rolling bearing which is used in aircraft, inparticular helicopters.

In aircraft, there are particular demands with regard to lightweightconstruction. For this reason, the rolling bearings which are used inthese aircraft also have to satisfy the demands relating to lightweightconstruction. Given the constantly increasing demands on the performanceof the rolling bearings, the problem has arisen that consequentlyconventional, fully hardening rolling bearing steels can no longer beused, on account of the possibility of cracks occurring under highloads.

DE 8711624 U shows a rolling bearing for aeronautical applications whichsatisfies the requirements for a lightweight construction yet is in aform which is very difficult to produce. Despite the complex form ofthis rolling bearing or of the rolling bearing races or raceways, thedemands imposed with regard to the possibility of the formation ofcracks being minimized are not satisfied by this embodiment.

OBJECT OF THE INVENTION

Therefore, the object is to propose a process for thin-walled rollingbearing raceways in aeronautical applications in which the risk ofcracking is reduced.

DESCRIPTION OF THE INVENTION

According to the invention, the object is achieved by a single-row ormulti-row rolling bearing comprising thin-walled bearing races which aremade of a martensitic, through hardened steel and having the followingcharacteristics: a surface hardness of ≧613 HV (56 HRC) in the area ofthe bearing face; a core hardness of ≧285 HV (28 HRC); a difference of≧150 HV (9HRc) between the surface hardness and the core hardness. Thecore hardness is reached at a depth ranging between 8 percent of thediameter of the rolling elements and 90 percent of the wall thickness onthe bottom of the track. There is a ratio of ≧20 between the diameter ofa pitch circle T_(k) and the diameter of a rolling element D_(w).

The core concept of the invention consists in the raceways of therolling bearing being surface-hardened. This surface-hardening makes itpossible to considerably reduce the risk of cracking even when usingthin-walled materials. The lower core hardness of the raceways preventsany cracks which may form originating in the running surfaces or in therolling contact from propagating further.

Particularly positive properties are produced for the rings according tothe invention if they have a surface hardness in the region of theraceways of ≧613 HV (56 HRC) and a core hardness in the thin-walledrings of ≧285 HV (28 HRC). The core hardness is reached at a depth ofbetween 8% of the rolling body diameter and 90% of the wall thickness ofthe race in the race base.

In this context, raceways are described as thin-walled if the ratio ofthe pitch circle diameter (T_(k)) to the rolling body diameter (D_(w))is greater than or equal to 20 (T_(k)/D_(w)≧20).

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a single-row groove ball bearing in section;

FIG. 2 shows a two-row angular ball bearing in section.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a single-row groove ball bearing 1. The outer ring 3, theinner ring 4 and the rolling bearings 6 are illustrated. The region withthe surface hardness 7 of ≧613 HV is indicated in the drawing around theregion of the race. The region having the core hardness 8 adjoins theregion having the surface hardness 7. The location of the pitch circlediameter T_(k) and the rolling body diameter D_(w) are shown in thedrawing. The pitch circle diameter T_(k) is based on the center point oftwo opposite balls.

FIG. 2 illustrates a two-row rolling bearing in the form of a two-rowangular ball bearing. The common outer ring 5 comprises two races inwhich the balls 6 roll. This two-row angular ball bearing 2 has twoinner rings 4. The position of the pitch circle diameter T_(k) and ofthe rolling body diameter D_(w) are indicated similarly to in FIG. 1.The region having the surface hardness of ≧613 HV is illustrated in theregion of the race and of the inner ring 4 and also of the outer ring 5.The contiguous region having the surface hardness made up of twoadjacent races 7 a is illustrated. In components having two races, thereis also the possibility of the region having the surface hardness 7being positioned separately around the races.

1. A single-row or multi-row rolling bearing having thin-walled races,wherein an inner and outer races each having a respective runningsurface for rolling bodies between the races, the races having a coreregion outward of the running surfaces, the races are comprised of amartensitic, through hardened steel and also having the followingfeatures: a surface hardness of ≧613 HV (56 HRC) in the regions of therunning surfaces of the race, a core hardness of ≧285 HV (28 HRC) of therace, a difference (Δ) between the surface hardness and the corehardness of ≧150 HV (9 HRC), the core hardness being reached at a depthinto each race of between 8% of a diameter of rolling bodies between theraces and 90% of a wall thickness in a race base beneath the runningsurface, and a ratio of a pitch circle diameter T_(k) of the bearing tothe rolling body diameter Dw of ³
 20. 2. The rolling bearing as claimedin claim 1, wherein the hardness at a depth of 4% of the rolling bodydiameter Dw is at most 70 HV (4 HRC) lower than at the surface.
 3. Therolling bearing as claimed in claim 1, wherein the races are of acorrosion-resistant steel.
 4. The rolling bearing as claimed in claim 1,further comprising at least one of securing flanges and reinforcingelements at the races.
 5. The rolling bearing as claimed in claim 1,further comprising rolling bodies between the races and rolling on therunning surfaces, the rolling bodies are of through hardened,martensitic rolling bearing steel, or of surface-hardened steel, or ofcorrosion-resistant steel or of ceramic.
 6. The rolling bearing asclaimed in claim 5, further comprising rolling bodies between the racesand rolling on the running surfaces, and the rolling bodies are balls.7. The rolling bearing as claimed in claim 5, further comprising rollingbodies between the races and rolling on the running surfaces, and therolling bodies are rollers.
 8. The rolling bearing as claimed in claim1, further comprising rolling bodies between the races and rolling onthe running surfaces.